Generally, a boom is a pole-like structure that is used to lift or support a load. The boom extends from a first terminal end to a second terminal end. In one type of boom, the first terminal end is adapted to engage a platform and the second terminal end is adapted to move relative to the first terminal end. The engagement between the first terminal end of the boom and the platform may be rigid such that the boom has no rotational degrees of freedom relative to the platform or from one to three rotational degrees of freedom relative to the platform.
In one type of boom, the second terminal end of the boom can be moved towards or away from the first terminal end of the boom. A first sub-type of boom in which the second terminal end can be moved in this manner is a hinged boom. A hinged boom includes a first sub-boom that defines the first terminal end of the boom, a second sub-boom that defines the second terminal end of the boom, and a hinge structure that connects the first and second sub-booms and allows rotational movement between the first and second sub-booms.
A second sub-type of boom in which the second terminal end of the boom can be moved relative to the first terminal end of the boom is a telescoping boom. In a telescoping boom the second terminal end of the boom is adapted to move linearly relative to the first terminal end of the boom. In one embodiment, the telescoping boom is comprised of two sub-booms, the first sub-boom defining the first terminal end of the boom and the second sub-boom defining the second terminal end of the boom. The first sub-boom defines a hollow space that is capable of accommodating a substantial portion of the length of the second sub-boom. A motor system (hydraulic, pneumatic, mechanical etc.) is employed to extend and retract the second sub-boom relative to the first sub-boom. Telescoping booms with more than two sub-booms are also known.
A third sub-type of boom in which the second terminal end of the boom can be moved relative to the first terminal end of the boom is a telescoping boom in which the second terminal end of the boom: (a) moves linearly relative to the first terminal end of the boom and (b) rotates about the longitudinal axis of the boom during any linear movement. In particular embodiments of this type of boom, the boom is a lattice/truss structure comprised of multiple longerons that generally extend in the longitudinal direction of the lattice/truss structure, multiple battens that each engage the longerons and extend substantially transverse to the longerons, and multiple diagonals that each extend between two consecutive battens such that the diagonal is not substantially perpendicular to either the battens or the longerons. In one particular embodiment, the longerons are each continuous between the first and second terminal ends. Each longeron is made of a material that allows the longeron or any portion of the longeron to be placed in a first unstrained state or a second strained state. When such a longeron or a portion of the longeron is in the first unstrained state, the longeron or portion of the longeron extends linearly and is capable of maintaining this shape over a range of loads. When the longeron or portion of the longeron is in the second strained state, the longeron or portion of the longeron has been subjected to a force that has caused the longeron or portion of the longeron to adopt a curved shape and store strain energy. The battens are also capable of being deformed between such first and second states. The diagonals are typically made of a flexible material (e.g., thread, wire etc.). The deformable nature of the longerons and battens allows the truss to be coiled. Further, the strain energy stored in the longerons and, to a lesser extent, the battens allows the truss to self-deploy such that the second terminal end of the truss moves linearly away from the first terminal end of the truss and, in so doing, also rotates about a longitudinal axis between the first and second terminal ends. Examples of this type of telescoping boom can be found in U.S. Pat. No. 3,486,279 and U.S. Pat. No. 4,866,892.
In another embodiment of a boom in which the second terminal end of the boom moves linearly relative to the first terminal end of the boom and rotates about the longitudinal axis of the boom during any such linear movement, each of the longerons is comprised of sub-sections that are connected to one another by lockable hinges. When the hinges are unlocked, the longerons and the truss can be coiled. When the hinges are locked, the longerons extend linearly. This particular embodiment of a telescoping boom does not store energy in the longerons or battens when coiled. As such, this particular embodiment of a telescoping boom requires some kind of motor mechanism to move the second terminal end of the boom relative to the first terminal end of the boom.